Incandescent lamp with internal fuse

ABSTRACT

An incandescent lamp having a coiled-coil filament connected to at least one formed spud, which is embedded in a pinch seal, contains at least one fuse member internal to the lamp envelope. The fuse member has a coiled portion which is connected to the spud and a leg portion which is connected to a lead-in conductor.

United States Patent Cardwell, Jr. Feb. 4, 1975 [54] INCANDESCENT LAMPWITH INTERNAL 3,211,943 10/l965 Cardwell 315/74 X FUSE 3,211,950 10/1965Cardwell ,1 315/74 3,346,768 10/1967 Patsch 315/74 [75] Inventor: J01lllG. Cardwell, .lr., Kirtland,

Ohm Primary Examiner-Gerard R. Strecker [73] Assignee: General ElectricCompany, Attorney, Agent, or Firm-Emi1 F. 805, Jr.; LawrenceSchenectady, N.(. R. Kempton; Frank L. Neuhauser [22] Filedi Aug. 1,1973 [21] App]. No.: 384,744 1 ABSTRACT I An incandescent lamp havmg acoded-coil filament connected to at least one formed spud, which is em-[52] U.S.Cl. 315/74, 313/315 bedded in a pimh Sea], contains at one fuse[51] I111. C1. T1011: 1/66 member internal to the lamp envelope. Thefuse [58] Fltld of Search 315/74, 313/315 ber has a coiled portion whichis cnnnected to [he [5 e e ce Cited zgltilcj'igre leg portion which isconnected to a lead-in UNITED STATES PATENTS 3,211,942 10/1965 Wiley313/315 7 3 1 INCANDESCENT LAMP WITH INTERNAL FUSE BACKGROUND OF THEINVENTION 1. Field of the Invention The invention relates generally toincandescent lamps. More particularly, the invention relates toincandescent lamps having a fuse member internal to the lamp envelope.

2. Description of the Prior Art It has been common practice to provide afuse for certain high efficiency tungsten-halogen type lamps becausethese lamps have a tendency to develope an ionized are which causes aflow of high current as is more fully described in Wiley U.S. Pat. No.3,21 I942. Two such fuse devices are described in Cardwell US. Pat. Nos.3,2l 1,943 and 3,2l l ,950, assigned to the assignee of the presentinvention. Both fuse constructions referred to above are internal to thelamp envelope which means that any are which occurs at lamp filamentfailure will be quenched inside the envelope.

By contrast, there are lamp constructions having external fuse designssuch as illustrated in US. Pat. No. 3,274,426. The disadvantages of thistype of construction are the number, complexity and expense of the partswhich must be assembled and the necessity for the are which commencesinside the lamp to continue through the lamp pinch seal before it isinterrupted by the fuse located in the base, external to the envelope.

Certain lamp applications require a very fine small diameter wire tomake a coiled-coil. The same applica tions also require a small diameterwire fuse. Prior art fuse constructions mentioned above are not readilyadaptable to these fine wire type lamps. Because of the delicate natureof the filament wire, it might easily break while in transit or duringother handling. Furthermore, wire which is very thin does not lenditself for threading a fuse member onto a coiled'coil, such as anoverwind, as shown in Cardwell US. Pat. No. 3.2l L943.

Consequently, formed spuds, such as .I-hooks or helispuds, are insertedinto the ends of the coiled-coil to give stability to the fine wirefilament. J-hook spuds or supports are more fully described in US. Pat.Nos. 3,44l,772 and 3,441,776. These spuds are metal conductors with acurved portion which fits inside a portion of the first secondary turnof the coiled-coil or a primary leg. Although the formed spud is a goodconductor and gives mechanical support to the filament, thisconstruction has the disadvantage of conducting heat back into the sealarea thereby causing foil shaling and other forms of seal failure.Another problem with formed spuds is because of their relatively largediameter the spud makes a good electrode to conduct the are when thefilament fails.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide a lamp with an internal fuse which will protect the lamp circuitfrom high amperage damage. A further object of the invention is toprovide a fuse internal to the lamp envelope so that any are may beterminated at the earliest possible moment. Still another object of theinvention is to provide a fuse construction with a minimum number ofparts and a minimum number of manufacturing steps to assemble the lamp.Yet another object of the invention is to provide an internally fusedlamp with a formed spud construction which gives good mechanical supportand precise location to the filament.

The objects of the invention are achieved by providing a lamp comprisedof a vitreous envelope of glass or quartz having a pinch seal at leastat one end thereof. Contained within the envelope is a filamentpreferably of tungsten and preferably of the coiled-coil variety. Atleast one end of the filament is connected to a formed spud through theinsertion ofa curved end of the spud into a portion of the primary turnof the filament.

The other end of the formed spud is sealed into the pinch seal toprevent any movement. A fuse member containing a coiled portion and aleg portion is positioned on the spud by inserting a straight section ofthe spud into the coiled portion of the fuse and by attaching the coiledportion to the straight section by a process such as welding. The legportion of the fuse is then attached to a lead-in conductor, a portionof which is usually a foliated piece of molybdenum. The lamp is thenexhausted and filled with an inert gas and a halogen.

BRIEF DESCRIPTION OF THE DRAWING FIG. I of the drawing is a frontelevation view of a lamp of the invention having one fuse;

FIG. 2 is a front elevation of a section of the lamp shown in FIG. I;and

FIG. 3 is a front elevation view of another embodiment of the inventionutilizing two fuses and a support.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 of thedrawing, lamp I0 is comprised of a tubular envelope II having pinchseals 12 and I8 at each end. Even though the preferred embodiment isshown as a double-ended lamp containing two pinch seals, it should beremembered that a singleended lamp, one pinch seal, may alsosuccessfully utilize the invention. Coil-coiled tungsten filament I3 isconnected to formed spuds, helispuds, l4 and 15. These spuds arepreferably made of tungsten. The spuds are inserted into the secondaryturns of the fila ment, as shown at 16 and 17. The end of the spud iscurved so that when it is inserted it will penetrate about one-half turnof the secondary coil.

Helispud I4 is sealed in insulating relationship to molybdenum foil 19which is hermetically sealed in pinch seal I8. Molybdenum foil I9 isconnected to outer lead 20 which makes electrical contact to a powersource. not shown, through tab 2]. Insulating base 22 is held firmly inplace on pinch seal 18 by a quantity of cement 23.

At the other end of envelope ll, helispud 15 which is attached tocoiled-coil I3 at location I6 is connected to foil 29 in pinch seal 12.Referring now to both FIGS. 1 and 2, fuse member 25 is comprised ofcoiled section 26 and leg portion 27. Coiled section 26 should have morethan one turn of wire to facilitate supporting the formed spud andmaking electrical contact with it. Although not entirely necessary topractice the invention, several of the coiled segments are attached tothe spud to further facilitate contact and support as shown at 28 inFIG. 2.

Leg portion 27 extends into pinch seal 12 and is attached to molybdenumfoil I9. The foil in turn is connected to outer lead-in conductor 20 andtab 2l. Insulating base 22 is attached to the tab and pinch seal bycement 23.

Test data from lamps of the construction illustrated in FIG. 1 indicatesthat lamps using a helispud and fuse member such as 25 have improvedlife over a construction which does not utilize the fuse but merelyutilizes helispuds attached directly to foil leads. Most of theimprovement appears to be due to the reduction in foil failures causedby excessive heat being conducted back to the foil from the relativelyheavy helispud.

One of the lamp types used in testing is a LOGO-watt. IZO-volt designknown as a DXW. In this lamp, the fuse was made of tungsten wire with a0.0l5-inch diameter, and it was attached as shown at 28 to a helispud ofapproximately 0.032-inch diameter. The particular fuses used had aminimum of five turns in the coiled section 26. With five turns, thisallows welding of one or more turns to the spud but at the same timekeeps a number of turns available if the welded turns would fracture dueto tungsten embrittlement. The other turns could continue to support andmake contact with the helispud.

A further improvement in lamp life was noticed when lamps similar to theconstruction of lamp 40, shown in FIG. 3. had two fused helispuded endsinstead of one. The lamp shown in FIG. 3 is basically the same as thatshown in FIGS. 1 and 2, and like parts are designated by like numeralsexcept the numbers in FIG. 3 are followed by the letter a.

Coiled-coil 13a is connected to helispuds 14a and 1511 through insertionof a curved portion of the helispuds into the secondary turns such as at160. The other ends of helispuds 14a and 150 are embedded in pinch seals12a and 18a in insulating relationship to foil conductors 19a and 29a.

Fused members 250 are attached to the helispuds by welding. for example.at locations 280. Coiled section 26a of the fuse is shown as having aplurality of turns generally more than five. Fuse legs 27a are attachedto foil conductors 19a and 290 which in turn make electrical contactwith tabs 21a and 31a through outer conductors a and 30a. Insulatingbases 22a and 32a are held to the pinch seals and tabs by cement 23a and33a. Coil support 35 is used to give the filament additional stabilityand to prevent sagging. The ends of the support are anchored in therespective pinch seals.

As indicated earlier, the presence of two fuses in the lamp improves thelife over lamps using one or no fuses, presumably because foil sealtemperatures are low ered and the probability of premature seal failureis greatly reduced.

A lamp construction using two fuses is desirable for ("ill yet anotherreason. When two fuses are used. they are connected in series andtherefore each fuse has only half the voltage across it. This in turnreduces the tendency of arcing at the fuse itself.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

I. An electric incandescent lamp comprising an envelope of vitreousmaterial having at least one pinch seal at one end of the envelope, anincandcscible filament of the coiled-coil type made of fine wireconnected at one end to a formed spud. said spud having its opposite endsealed in said pinch seal in insulating relationship to a lead-inconductor, and a fuse member electrically connected to the spud at oneend and a lead-in conductor at the other end. said fuse membercomprising a coiled portion fitted over the formed spud which is sealedin said pinch seal and a leg portion, said leg portion being attached toa foliated section of the lead-in conductor, said filament beingunsupported by said fuse member.

2. An incandescent lamp as claimed in claim 1 wherein said coiledportion of said fuse has five or more turns.

3. An incandescent lamp as claimed in claim I wherein said coiled-coilfilament is supported by a coil support which has its ends sealed insaid pinch seals.

4. An incandescent lamp as claimed in claim 1 wherein said coiledportion of said fuse has more than one full wire turn.

5. An incandescent lamp as claimed in claim I wherein a part of saidcoiled portion of said fuse is attached to the formed spud.

6. An electric incandescent lamp comprising a tubular envelope ofvitreous material having pinch seals at each end, an incandesciblecoiled-coil filament made of fine wire, said filament connected at eachend to a formed spud, the opposite ends of the spuds being sealed insaid pinch seals in insulating relationship to lead-in conductors. andfuse members connected to each spud at one end and a lead-in conductorat the other end. said lead-in conductor being hermetically sealed insaid pinch seals, said fuse members comprising a coiled portion fittedover the spuds and a leg portion. said leg portion being attached tosaid hermetically sealed lead-in conductors. said filament beingunsupported by said fuse members.

7. An incandescent lamp as claimed in claim 6 wherein said coiled-coilfilament is supported by a coil support which has its ends sealed insaid pinch seals.

1. An electric incandescent lamp comprising an envelope of vitreousmaterial having at least one pinch seal at one end of the envelope, anincandescible filament of the coiled-coil type made of fine wireconnected at one end to a formed spud, said spud having its opposite endsealed in said pinch seal in insulating relationship to a lead-inconductor, and a fuse member electrically connected to the spud at oneend and a lead-in conductor at the other end, said fuse membercomprising a coiled portion fitted over the formed spud which is sealedin said pinch seal and a leg portion, said leg portion being attached toa foliated section of the lead-in conductor, said filament beingunsupported by said fuse member.
 2. An incandescent lamp as claimed inclaim 1 wherein said coiled portion of said fuse has five or more turns.3. An incandescent lamp as claimed in claim 1 wherein said coiled-coilfilament is supported by a coil support which has its ends sealed insaid pinch seals.
 4. An incandescent lamp as claimed in claim 1 whereinsaid coiled portion of said fuse has more than one full wire turn.
 5. Anincandescent lamp as claimed in claim 1 wherein a part of said coiledportion of said fuse is attached to the formed spud.
 6. An electricincandescent lamp comprising a tubular envelope of vitreous materialhaving pinch seals at each end, an incandescible coiled-coil filamentmade of fine wire, said filament connected at each end to a formed spud,the opposite ends of the spuds being sealed in said pinch seals ininsulating relationship to lead-in conductors, and fuse membersconnected to each spud at one end and a lead-in conductor at the otherend, said lead-in conductor being hermetically sealed in said pinchseals, said fuse members comprising a coiled portion fitted over thespuds and a leg portion, said leg portion being attached to saidhermetically sealed lead-in conductors, said filament being unsupportedby said fuse members.
 7. An incandescent lamp as claimed in claim 6wherein said coiled-coil filament is supported by a coil support whichhas its ends sealed in said pinch seals.